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Re: std::regex: inserting std::wregex to std::vector loses some std::wregex values
- From: Paolo Carlini <paolo dot carlini at oracle dot com>
- To: Tim Shen <timshen at google dot com>
- Cc: Jonathan Wakely <jwakely dot gcc at gmail dot com>, Stefan Schweter <stefan at schweter dot it>, libstdc++ <libstdc++ at gcc dot gnu dot org>
- Date: Sun, 14 Sep 2014 20:29:07 +0200
- Subject: Re: std::regex: inserting std::wregex to std::vector loses some std::wregex values
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- References: <540C6873 dot 9030205 at schweter dot it> <CAH6eHdSdmAdo420reU92ujW+nT63H431vsuP9YzZo5YQPj1T3A at mail dot gmail dot com> <CAG4ZjNkti0p=XAdhDYeXbcUx3mtqxH4P-U5F9DXmahG1=0b1Dg at mail dot gmail dot com> <CAG4ZjNmwG1VYrA2cnw7_hhxcHukC01U-DOzfpdjbZhcLgLP_sQ at mail dot gmail dot com> <54156B0B dot 2050006 at oracle dot com> <CAG4ZjNm_PzVYhyonUGOq3fMK8Drj9FNseXepKCts_SGzF=LSkQ at mail dot gmail dot com>
Hi,
On 09/14/2014 08:12 PM, Tim Shen wrote:
On Sun, Sep 14, 2014 at 3:16 AM, Paolo Carlini <paolo.carlini@oracle.com> wrote:
Thus, are you going to send an actual patch? I'm wondering if we could
arrange it in such a way not to break the binary compatibility in the
release branch (thus fix the bug there too) perhaps by not removing any data
members, simply leaving them unused?! In mainline I suppose we are going to
stabilize the ABI for the 5.0 release, thus we can do that. While we are at
it, check that the order of the final remaining data members is still
optimal size-wise.
I've made a patch that changes basic_regex's member only, by making
basic_regex::_M_traits heap allocated.
Thanks. Maybe Jon can have a closer look to it...
I believe that I didn't get it, but I'm still a little bit confused,
since we haven't instantiated and exported any regex class (except
regex_error, I suppose) to the binary, right?
Anyway, the patch is bootstrapped and tested with debug flag. Can it
be modified slightly to keep the binary compatibility?
Probably yes, but then, as described here:
https://gcc.gnu.org/onlinedocs/libstdc++/manual/abi.html
under <prohibited changes>, you cannot add or remove the basic_regex
data members. This doesn't have much to do with the exported symbols,
the mental model is somebody including the old <regex> compiling an a.o,
then including the new <regex> and compiling a b.o, then linking
together a.o and b.o: things must work fine in every case.
Paolo.